Towards understanding of the interaction of certain carbapenems with protein via combined experimental and theoretical approach.

The interactions of the recent carbapenems; ertapenem (ERP) and meropenem (MRP); with serum albumin (SA) were closely investigated by a combined spectrofluorometric experimental and theoretical approach. The approach is based on the quenching of fluorescence intensity of bovine serum albumin (BSA) upon binding with different carbapenems. The quenching was observed at λem 333-340 nm after excitation at 280 nm. Mechanism of interaction was found to be static quenching through hydrophobic and H-bonding interactions and confirmed with molecular docking using MOE software. Binding constant, binding number were estimated for both MRP and ERP. Thermodynamic parameters including entropy change (ΔS), enthalpy change (ΔH) and free energy change (ΔG) were calculated at three different temperatures. Moreover, BSA configuration during binding was investigated via synchronous and 3D spectrofluorimetry. Förster resonance energy transfer calculated (FRET), integration interval (J) and distance (ro) between BSA and the studied drugs were calculated to confirm the static quenching.